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Probably going to purchase a sixty plus year old house. It has a gas furnace in the basement and the house is about 2500 sq. feet, two story. I need to add air to the house as it is located in Western Kentucky. The humidity will melt me
Am wondering if I can add onto the existing heating system, or if I have to put in a whole new system???? Wondering what modifying the existing system might run in cost??????
It depends. You have a gas furnace but does it have forced air vents (I am assuming yes). You should be able to add on to that if the ductwork is correct. Cost $2500-5000 ballpark (in our area anyway). You might need to upgrade the electrical to handle the load which could run another $1500 or so (for the whole house which is a good idea anyway).
Yes, usually you can just add A/C to an existing heating duct system but maybe you do not want too. Lot depends on how old your heating plant is.
Try this lil rule of thumb test. With the heat turned on and running put your hand on the outlet flue pipe coming out of the furnace going to the chimney. Can you comfortably keep your hand on the flue pipe? With the old furnaces most times not, they are running >135 F and a lot of BTU's are going up the chimney. You are wasting a lot of fuel.
The better approach is survey the entire house for weather proofing. You want the entire envelop around the house as leak proof as possible and a good insulation job.
You start in the attic and put in a good under roof air flow system, this allows air to flow from the soffit vents up under the roof and vent out ridge / end wall vents. The goal is never to let the attic volume heat up very much, one goal is say no more than 20 degrees greater than outside ambient temperature. By using the under roof air flow system along with proper insulation should be able to do it. This cuts the A/C total load a lot.
Same with around the rest of the house, find and fix all air leaks, consider new energy efficient windows and doors, upgrade insulation in walls. It is important to disassemble the window trim if doing replacement windows, old houses leak a lot around the window frames, you need to get into the crannies and insulate all of it.
If you get the house energy tight, then you can upgrade the furnace with a new modern high efficiency model and add A/C piggy back off that. The new furances are like 95+% efficient, their exhaust flue gas is so cold they use a PVC pipe instead of the old chimney. They take cold air in via another PVC pipe for combustion air from the outside.
The thing about this approach, if the house has been made very efficient, you can down grade the burner size compared to the old furnace, saving even more fuel. Your A/C unit will not have to be as big either. You get the money back pretty quick.
Example I did this with an old house, total make over to get it very insulated, air tight. New high efficient furnace, under roof air flow system in attic, upgrade of all the existing insulation, got all the air leaks, new windows, doors. Cost me a tad over $6000. Was able to derate the new burner from an old 270,000 BTU natural gas burner to only 70,000 BTU piezo ignition burner in a new replacement high efficiency furnace. The old burner was with a pilot light that also wasted a ton of energy. Probably half of all the BTU's were just going up the chimney. My energy bills are probably about a 1/4 of what the prior owner's were.
I don't really need A/C. Got some window units but don't even use those, couple window fans normally keep the house very comfortable. But in your case if you get the house very tight, you can get away with a much smaller installed A/C unit. You spend a lil up front but quickly get the money back on operating costs and the house is far, far more comfortable.
Try to work with Mother Nature and not just use brute force heating / cooling techniques. It can put you in the poor house pretty quick.
Yes, usually you can just add A/C to an existing heating duct system but maybe you do not want too. Lot depends on how old your heating plant is.
Try this lil rule of thumb test. With the heat turned on and running put your hand on the outlet flue pipe coming out of the furnace going to the chimney. Can you comfortably keep your hand on the flue pipe? With the old furnaces most times not, they are running >135 F and a lot of BTU's are going up the chimney. You are wasting a lot of fuel.
The better approach is survey the entire house for weather proofing. You want the entire envelop around the house as leak proof as possible and a good insulation job.
You start in the attic and put in a good under roof air flow system, this allows air to flow from the soffit vents up under the roof and vent out ridge / end wall vents. The goal is never to let the attic volume heat up very much, one goal is say no more than 20 degrees greater than outside ambient temperature. By using the under roof air flow system along with proper insulation should be able to do it. This cuts the A/C total load a lot.
Same with around the rest of the house, find and fix all air leaks, consider new energy efficient windows and doors, upgrade insulation in walls. It is important to disassemble the window trim if doing replacement windows, old houses leak a lot around the window frames, you need to get into the crannies and insulate all of it.
If you get the house energy tight, then you can upgrade the furnace with a new modern high efficiency model and add A/C piggy back off that. The new furances are like 95+% efficient, their exhaust flue gas is so cold they use a PVC pipe instead of the old chimney. They take cold air in via another PVC pipe for combustion air from the outside.
The thing about this approach, if the house has been made very efficient, you can down grade the burner size compared to the old furnace, saving even more fuel. Your A/C unit will not have to be as big either. You get the money back pretty quick.
Example I did this with an old house, total make over to get it very insulated, air tight. New high efficient furnace, under roof air flow system in attic, upgrade of all the existing insulation, got all the air leaks, new windows, doors. Cost me a tad over $6000. Was able to derate the new burner from an old 270,000 BTU natural gas burner to only 70,000 BTU piezo ignition burner in a new replacement high efficiency furnace. The old burner was with a pilot light that also wasted a ton of energy. Probably half of all the BTU's were just going up the chimney. My energy bills are probably about a 1/4 of what the prior owner's were.
I don't really need A/C. Got some window units but don't even use those, couple window fans normally keep the house very comfortable. But in your case if you get the house very tight, you can get away with a much smaller installed A/C unit. You spend a lil up front but quickly get the money back on operating costs and the house is far, far more comfortable.
Try to work with Mother Nature and not just use brute force heating / cooling techniques. It can put you in the poor house pretty quick.
Where do you live that you can get buy without AC? I don't care how tight your house is, summers here can be very hot and humid-there is no way I would live without AC with 90°+ temps during the day cooling off to 80° at night with high humidity .
Where do you live that you can get buy without AC? I don't care how tight your house is, summers here can be very hot and humid-there is no way I would live without AC with 90°+ temps during the day cooling off to 80° at night with high humidity .
Well it is in Ohio. But not all parts of Ohio are like this, you got to pick the spots carefully, we really don't get much humidity. Up in elevation, typically doesn't get steaming hot either. Plus I got a tree to shade part of the south side, and I have the house set up to take advantage of the cooler air that occurs on the North side, the window fans have built in thermostats and auto cycle.
There are a zillion tricks too it. Each house might require a bit different approach. The last house I had in Boston, was not anywhere close to energy tight and that place gets humidity and God awful heat in summer. No spring, just baking summers with tourists and kids with dripping ice cream cones, sweating with humidity. Not like them tourist guide books say.
But I solved that one by making a large opening up into the attic. Tall house, opened a big attic window, kept all the other windows in the house closed, including all the storm windows, pulled all the shades on the southern side. Then cracked the basement entry door a tad. That allowed the house to set up a natural circulation type air flow that sucked the cool air up out of the basement thru the house and out the attic window. Again I had the window A/C's but rarely used them. The other benefit was the attic volume never got steaming hot, you could go up there on the hottest day and run around, maybe a bit over 100F. The "cool of the house" lasted enough to stay fairly comfortable most days without any A/C.
So when the sun went down and night air was cool, I could just run window fans and blow cool air into the house and out that same flow path thru the attic. Part of it can be "shifting the thermal cycle of the day" to use Mother Nature to the best advantage.
Way too much thinking the only solution is brute force cooling. You see it a lot in Florida, they never build it right in the first place, then it is only brute force with hugemumgous big A/C units. Must be a power company conspiracy, they sure laugh all the way to the bank. Most folks never use the techniques that could help a lot. Lots of "Standard Thinking" and them experts never do anything that goes against their own interest either.
Lots of ways to skin the goat, you got to evaluate each house to determine what can work. Not normally what gets done. Geo-thermal is the way to go if you are doing a new house. Always use Momma Nature to the best advantage.
golfgal has a good point... if you go and install a/c right away and then make a bunch of changes to improve energy efficiency the air conditioner will be oversized and not run as much. That means your place is now more humid because the a/c isn't pulling as much moisture out of the air.
My vote goes for upping the efficiency first. Then once you've got that sorted out you can get a better idea about what size air conditioner is needed. You'll be able to get a smaller one and it'll cost less, perform better and use less power than if you go at it the other way around.
We have an old 2000 sq foot home with only central heat. We are wanting to add AC as well as update heating unit. Had two estimates this week.....one contractor will use existing duct work-which is metal, insulate it and add the new units. The other contractor wants to replace the duct work with flexible duct system. He says if it is not replaced there would not be enough air flow for the AC to operate without freezing up. The difference in cost is almost $5000. Any comments or suggestions. Thanks
Last edited by Sally Hulse; 06-25-2014 at 04:30 AM..
Reason: typo
one contractor will use existing duct work-which is metal, insulate it and add the new units.
The other contractor wants to replace the duct work with flexible duct system.
Needing to replace (some of) the trunk duct for sizing or condition or layout reasons is often valid.
I did exactly this myself just this year.
Replacing it with FLEX though... says you keep looking for a better operator.
And yeah, (if needed) it's worth the extra cost for metal.
The larger concern is RETURN duct sizing and registers.
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Maybe you want to take another approach
